The computer turn on for a while then screen turn back off

I left my computer on over night. later the next day i tried to turn on the laptop but the screen came on but after the computer warmed up, the screen turn blank. I leave it off for a an hour or two, the screen work for a couple of minute but the keyboard would not response. I see the light and fan turn on but the screen would not come on even when i connect it to a external monitor it is still the same. can you please give me some idea. thanks

You say you left it on all night and then when you came to turn it on.so who turned it of or why did it go off ?
you probably have missing sys files in which case ur gonna have to reinstall os to replace sys files( you aint the first,it happens many times for many different reasons)
usually with incorrect shut down ,especially when shut down when updating files;trouble is most of the time you dont know its updating cos its in the background.
boot up with os in cd tray choose install ,not repair .system checks disk and detects existing os ...now you can choose repair unless you opt for fresh install...that choice is yours.either way get you back in windows but repair gets you back before things went wrong with all software/files previously downloaded or saved intact.

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Face Recognition Usually you'll find the webcam at the top and middle of the laptop screen. One unique feature included with the webcam on newer Toshiba laptops including the Satellite Pro, Portege and Qosmio models is facial recognition. Instead of having to type in a password when you open the laptop, you can set up the computer to recognize your face and automatically load your settings. b> Setup b> To access the face recognition feature on a Toshiba laptop, open the laptop to the registration screen and click the Face Recognition icon. Look at the circle that appears on the screen and align your face so that it fits within the circle, and then click "Next." At the next page, enter your name and password and click "OK." The next time you use the computer, click on your Face Recognition icon from the main screen and look at the webcam so it can recognize your face and load your settings. b> Night Mode b> If you're in a low-light situation you can take advantage of the webcam's Night Mode effect. To turn it on, open the Camera Assistant by clicking the Start button, and then select "All Programs."

Select the "Camera Assistant" folder and then select the "Camera Assistant" software. Once it's open, hover your mouse over the far left hand side of your laptop screen. This will cause a number of webcam icons to appear. Click the "Properties" icon, which looks like a box with a pen over the top left of the box. Click the "Night Mode" check box from the Properties window and then click "OK." b> Other Profiles b> You can also alter other effects and features of the webcam from the Camera Assistant. First open the Camera Assistant by clicking the Start button, and then select "All Programs." Select the "Camera Assistant" folder and then select the "Camera Assistant" software. Then hover your cursor on the far left of the screen until you see the webcam menu appear, and select the "Properties" icon. Then click on an individual "Profile" tab to adjust the white balance, lower or raise the brightness, or correct the colors. As you click on the adjustment, you should see the change reflected in the way the webcam is displaying on your laptop. When you've selected the settings you want, click "OK" from the Profile window.

When you wake the computer up from sleep, eventually some of the windows files become corrupted. I recommend that a proper shut down be done when not in use. Now to try and address your problem, do a system restore and take it back in time before this started, if successful should resolve your issues.

Try to restart in safe mode with networking....hold down the F8 key during restart. If the computer reboots in safe mode, then go to system restore and restore the computer back a day or two. If this does not work, then try holding down F8 during reboot and scroll down and choose " Last Good Configuration".